An Antipodal Seismic and (Infra)acoustic View from Central Europe on the 15 January 2022 Hunga-Tonga-Hunga- Ha'apai Eruption

We present seismic and (infra)acoustic observations of the 15 January 2022 Hunga- Tonga-Hunga-Ha'apai (HTHH) eruption from Switzerland and central Europe at epicen-tral distances around 153 degrees. Our observations indicate that the efficient seismoacoustic coupling of locally confined atmospheric oscillations (at the volcanic plume) and long -reaching (global) atmospheric waves at frequencies around 4 mHz is responsible for the global seismic reach of the HTHH eruption at low frequencies. At high frequencies (HFs), we recorded many short impulsive seismoacoustic signals with frequencies well above 20 Hz. They coincided with the passage of the HF part of the rather low-frequency atmospheric wave and triggered numerous false local-earthquake detections on the Swiss monitoring system. Simultaneous reliable ear witness reports of thunderlike sounds from southwest Germany suggest that signals related to the eruption were audible in central Europe at a distance of more than 17,000 km from HTHH. We postu-late that the source of these HF seismoacoustic signals was the vigorous volcanic light-ning activity observed at HTHH.

Automated summary

We present seismic and (infra)acoustic observations of the 15 January 2022 Hunga- Tonga-Hunga-Ha'apai (HTHH) eruption from Switzerland and central Europe, providing insights into the global reach of the eruption through seismoacoustic coupling of atmospheric oscillations and atmospheric waves. High-frequency seismoacoustic signals coinciding with the passage of low-frequency atmospheric waves were recorded, triggering false local-earthquake detections. Thunderlike sounds were also reported in central Europe, suggesting that the vigorous volcanic lightning activity at HTHH was the source of these high-frequency signals.